Aerosol dispensing systems are known in which a flexible inner product container is positioned within a rigid outer container with the flexible inner container serving to separate the product from the propellant. In this type of aerosol system, known as a barrier pack, the product may be contained in the flexible inner container with the aerosol propellant in the region between the exterior of the flexible inner container and the interior of the rigid outer container. A dispensing cap is in communication with the flexible inner container and, on opening a valve, product within the flexible inner container may be discharged through the dispensing cap by the propellant pressure on the exterior of the flexible inner container.
A principal disadvantage of barrier pack aerosol systems involves the expense and difficulty in pressurizing the system with propellant. This is presently accomplished by providing a valve closure in the rigid outer container. The outer container may then be pressurized, by inserting propellant through the valve closure into the region between the flexible inner container and the rigid outer container.
The present procedure for pressurizing a barrier pack aerosol system with propellant is generally unsuitable for the mass production of aerosol dispensing systems. In particular, the position of the fill applicator and the valve closure in the outer container must be precisely aligned when propellant is charged through the valve closure. Also, the fill applicator and valve closure must be maintained in alignment as propellant is being charged to the outer container, since relative movement between the valve and the fill applicator could result in damage to the outer container or the valve closure to produce leakage.
In view of the above difficulties in present procedures for pressurizing a barrier pack aerosol system with propellant, it would be desirable if a procedure could be devised which would permit rapidly charging propellant to a barrier pack aerosol system on a mass production basis. Additionally, it would be desirable if such a procedure could be carried out with existing filling equipment such as undercap filling apparatus which is presently used in charging propellant to a conventional aerosol system in which the product and the propellant are mixed together, and are not separated by an inner container.